Acid treating wells



Jan. 2, mr v. vooRHEEs ACID TREATING WELL Filed Dec. 19, 1941 zZZ01/').-' Zmadewwewfweas B Quibmw lPatented Jan. 2, 1945 ACID TREATING WELLS Vanderveer Voorhees, Homewood, lll., assignor to Standard Oil Company, Chicago, Ill., -a corporation of Indiana Application December 19, 1941, Serial No. 423,579

(Cl. ISG- 25) 9 Claims.

This invention relates to the treatment of wells, particularly deep wells, for the production of oil, gas, water, brine or other uids to decrease the resistanze to iiow encountered by the duid in the geological formation or formations at or near the base of the Well. More particularly, the invention relates to the treatment of deep oilwells in order to cause, restore or increase oil production therefrom.

In the operation of wells, particularly oil wells, the original rate of flow tends to decrease after the Well is brought in, and even if 'the well produced freely at rst it is ultimately necessary to resort to pumping in order to maintain a satisfactory rate of production. Furthermore, even after pumping is resorted to, the rate of production tends to decline until it ultimately reaches a point at which it is no longer economical to continue the operation of the well. This point is very often reached long before the oil or other duid in the subterranean reservoir adjacent the well is exhausted. This may be due to various causes; one of the main causes being the clogging of the pores, crevices, capillaries and ow channels of the producing formation by the precipitation of fine grains of limestone or other mineral deposits, components of drilling muds, etc.

One method for treating deep Wells to increase the production thereof is the use of acids, the particular acid chosen depending upon the nature of the formation to be treated. Hydrochloric acid is commonly employed, the latterbeing particularly effective in the case of Wells sunk through calcareous formations. There are, however, several disadvantages in the use of hydrochloric acid or other aqueous acids in oil well treatment. One problem which seriously interferes with the beneficial use of this method is corrosion of the well casing and other exposed metal equipment. Also since the aqueous acids readily attack the mineral formations they tend to become neutralized or spent before they .penetrate to any great distance into the strata under treatment, and as a result the ediciency of the process is materially decreased.

An object of the present invention is to provide an efficient method of producing by an explosive Vchemical reaction. a formation-treating agent in situ in a well and utilizing the energy liberated to force the treating agent so produced into the surrounding formation. Another object of the invention is to provide a means for generating a treating acid in at least one formation surrounding the well. A further object of the invention is to provide a means of forming an acid in a well and forcing the same into at least one formation surrounding the well whereby production and ow of uid from the well are increased. Another object of the present invention is to provide an efficient means of forming hydrochloric acid in situ in a well and utilizing the sameto act upon calcareous formations surrounding said well to increase the ow of uid therefrom. Another object of the invention is to provide a method of forming a formation-treating agent and carbon in situ in a well and whereby the latter coats the capillaries, crevices and the like of the Wellso that the same are preferentially wetted by oil. Other objects and advantages of the invention will become apparent from the following description thereof read in conjunction with the accompanying drawing which forms a part of the specification and -in which Figure 1 is a vertical section of an apparatus for carrying out the invention; and

Figure 2 is a section through a well showing the apparatus shown in Figure 1, suspended therein.

In accordance with the present invention the desired mineral acid is formed in the well by an explosive acid-generating reaction, such as by causing hydrocarbons to react with a chemical reagent capable of forming the desired acid, when reacted With the hydrocarbons. For example, a halogen such as chlorine, is reacted with hydrocarbons to form a halogen acid, such as hydrochloric acid. The reactions of the type described are preferably made to take place in a destructible bomb so that the acids formed and forming will be frced into the surrounding strata by the explosive pressure. A preferred method of practicing the invention is to employ a bomb divided into two chambers by a destructible partition, lower the bomb containing the hydrocarbons and the reacting reagent in the separate chambers to the desired depth in the well and pierce the separating partition by suitable means to permit the mixing of the hydrocarbons with the reacting reagent. The reaction of the hydrocarbons with the reaction reagent, such as chlorine, is a very violent and explosive one which causes the destruction of the bomb and forces the acid formed into the surrounding strata. Carbon, which is formed by the interaction of the hydrocarbon and chlorine, is also forced into and coats the capillaries, crevices, etc. of the surrounding strata, making the surfaces of the same preferentially wetted by the oil and thereby enhancing the ow of oil through the same.

, Although any hydrocarbon can be used, I prefer 5 to employ low-boiling petroleum distillates such as petroleum naphthas, heavy naphtha, kerosene, gasoline, gas oil and the like, and particularly low-boiling cracked petroleum distillates.

.The method of carrying out the invention can best be described with reference to the accompanying drawing which illustrates one embodiment of the invention, and which is intended to be illustrative only.

Referring to the figures, a shell or cartridge I is made of two sections, an upper section II and a lower section I2 which are divided by a destructible membrane I3 forming an upper chamber I4 for receiving the heavier reaction component, and a lower chamber I5 for receiving the lighter reaction component. The lower section I2 is attached to the upper section II by a suitable means such as by a threaded joint. The lower section I2 is closed at the bottom by a cap I1 provided with a plug I8 which may be utilized for filling the chamber -I5. The upper section II is closed at the top with a screw cap I9 which is provided with a filling plug 20 and a gas-tight bearing 2| through which passes a plunger 22 provided with a tapered piercing end 23 and a ring-head 24, which is adapted to receive the cable for lowering the shell into the Well.

In operation the shell I0 containing the chemical reagent such as liquid chlorine in the upper chamber I4 and the hydrocarbon in the lower chamber I5 is lowered into the well (Figure 2) through the well casing 26 by means of a cable 21 which passed through the ring-head 24 of rod 22. When the shell has reached the desired depth the plunger 22 is forced =by suitable means such as a weight, through the membrane I3. This weight which is provided with a hole through the center thereof is guided down the well by the cable 21, which passes through the hole. The falling weight ring strikes the ringhead 24 of rod 22 forcing the tapered piercingend 23 through the membrane I3, causing the intimate commingling and solution of the chemical reagents such as chlorine and the hydrocarbon. The reaction between chlorine and hydrocarbon by which hydrochloric acid is formed is a violent, explosive one, and creates sulcient energy to explode the shell I0 and force the hydrochloric acid into the adjacent strata.

The shell I0 may be made preferably of a suitable shatterable material such as tin, brittle steel, Bakelite or various other materials. Under some conditions the reaction between the chemical reagent and the hydrocarbon material may not be sufliciently active to promote the explosion of the shell immediately. Under these circumstances it may be desirable to promote the explosion by means of a detonator action. For this purpose I may employ a secondary bomb or go devil carrying an explosive charge to be 4dropped on the chlorine-hydrocarbon bomb within the well. Likewise I may set off the explosion by suitable electrical means.

If desired the explosive force ofthe reaction of the hydrocarbon and the reagent may be supplemented by the use of various high explosives such as nitroglycerine, gun powder and the like, exploded simultaneously.

After the shell has been exploded and the product acid, for example gaseous hydrochloric acid, has been "shot into the surrounding strata, water or steam can be introduced into the Well to form aqueous hydrochloric acid which will attack the formation and wash away dissolved mineral obstructions. However, water present in the formation is usually adequate.

Alternatively to the above method of introducing acid forming materials into the well, I may release the liquid chlorine directly into the bottom of the well by opening a valve in the canister or bomb by which it is introduced. After supplying a quantity of liquid chlorine infthis way to a well containing a suitable hydrocarbon, the resulting mixture is forced into the formation. The mixture may then be allowed to detonate Aspontaneously or its detonation may be inaugurated by an explosive charge.

Instead of introducing the acid producing ma terials into the well by canisters, these may be forced into the well through tubing leading from the surface, although this is not usually preferred. For example, liquid chlorine can be pumped to the bottom of the well through a tube and mixed at that point with the desired hydrocarbon, for example, gasoline or crude oil already present in the well. A suitable mixing nozzle may be employed for obtaining the desired mixture ratio for the best results. The ratio of 4 volumes of liquid chlorine to 1 volume of hydrocarbon is effective. Gasoline for the purpose may be supplied to the well by pumping from the surface through the casing or through a separate tube. If desired the gasoline and chlorine may be mixed and forced into the formation while the 'well is filled with drilling mud, oil, or other liquid, the mud or other liquid serving to protect the casing from contact with the acid products and also serving to blanket the force of explosion resulting from the reaction. 'Ihe acid generating mixture may be forced through fissures in the formation for some distance from the well before detonating, thus opening an extended drainage system.

In addition to acidizing the formation at the bottom of a well, I contemplate attacking the formation at an intermediate point, if desired. Thus the mixture of halogen and hydrocarbon may be detonated at any point of elevation in the strata traversed by the well base. 'I'here is a denite advantage, particularly in this case, in having the well filled with a liquid. The shattering eifect'of the detonation reaction can be made to rupture the casing at the point in question, providing the Well has beencased, the simultaneous injection of acid vapor into the formation occurring too rapidly for the acid to become dissipated.

I have described my invention in terms of certain specific embodiments thereof but I do not desire to be limited thereby but only to the scope of the appended claims.

I claim:

1. The method of increasing the production of a well in which the flow of'iluid from the surrounding formation' is restricted, comprising introducing into said formation a liquid hydrocarbon and liquid chlorine and causing the liquid hydrocarbon and the liquid chlorine to explosively react whereby the hydrochloric acid formed by said reaction attacks the said formation.

2. The method of increasing the production o! a well in whichthe fiow of fluid from the surrounding formation is restricted, comprising introducing into said well a liquid halogen and a hydrocarbon liquid, mixing together the liquid halogen and the hydrocarbon liquid, combustively reacting said mixture, thereby forming the corresponding hydrohalogen acid, and attacking said formation with said acid.

3. The method described in claim 2 in which the halogen is chlorine.

4. The method of increasing the production of an oil well in which the ow of oil from the surrounding formation is restricted, comprising introducing a liquid halogen into said well, combustively reacting said liquid halogen with a liquid hydrocarbon in said well adjacent the restricting formation, thereby forming the corresponding hydrohalogen acid, and attachng said formation with said acid.

5. The method described in claim 4 in which 7. The method of increasing the production of a well in which the iiow of iiuid from the surrounding strata is restricted, comprising commingling in a shell a liquid hydrocarbon and a liquid halogen which explosively react to form an acid capable of dissolving the surrounding strata, whereby the explosive force of the resulting reaction shatters the shell, and the acid formed is forced into the surrounding strata.

8. The method described in claim 7 in which l 

